Transgenic mice carrying functional single nucleotide polymorphisms in brain-specific tryptophan hydroxylase

Abstract

Recombinant or transgenic non-human mammals are described having a mutant tryptophan hydroxylase 2 (Tph2) gene resulting in altered synthesis of 5-hydroxytryptophan and serotonin in the brain. In some embodiments the mutant tryptophan hydroxylase 2 gene contains mouse R439H and/or P447R functional mutations, or their corresponding mutations in other species. Congenic non-human mammals having mutant tryptophan hydroxylase 2 genes are also provided. Methods of screening a compound for serotonergic activity or activity in treating a serotonergic neurotransmission dysregulation disorder are provided, which include administering a test compound to a recombinant non-human mammal and then detecting the presence or absence of serotonergic activity, or activity in treating a serotonergic neurotransmission dysregulation disorder, in the mammal. A cell such as a nerve cell (e.g., a central nervous system neuron) isolated from a transgenic or congenic mammal is also disclosed, along with cell cultures containing these cells.

That which is claimed is: 
     
       1. A transgenic mouse comprising a mouse R439H mutant tryptophan hydroxylase 2 (Tph2) transgene, which replaces endogenous Tph2 in the genome of said mouse, wherein said mouse is homozygous for the transgene, wherein said transgene results in reduced synthesis of 5-hydroxytryptophan (5-HTP) and reduced levels of serotonin in the brain of said mouse as compared to a wild-type mouse, and wherein said mouse exhibits a behavioral phenotype of a serotonergic neurotransmission dysregulation disorder as compared to a wild-type mouse. 
     
     
       2. The transgenic mouse of  claim 1 , wherein said serotonergic neurotransmission dysregulation disorder is depression. 
     
     
       3. The transgenic mouse of  claim 2 , wherein the behavioral phenotype of depression comprises behavioral despair. 
     
     
       4. The transgenic mouse of  claim 3 , wherein the behavioral despair is evidenced by increased immobility in a tail suspension test as compared to a wild-type mouse. 
     
     
       5. The transgenic mouse of  claim 4 , wherein the increased immobility can be reduced by administration of thiadiazolidinone. 
     
     
       6. The transgenic mouse of  claim 4 , wherein the increased immobility can be reduced by administration of fluoxetine. 
     
     
       7. The transgenic mouse of  claim 1 , wherein the synthesis rate of 5-HTP is reduced by at least 70% in the brain of said mouse as compared to a wild-type mouse. 
     
     
       8. The transgenic mouse of  claim 1 , wherein said transgene results in reduced synthesis of 5-HTP in the frontal cortex and hippocampus of said mouse as compared to a wild-type mouse. 
     
     
       9. The transgenic mouse of  claim 1 , wherein the synthesis rate of serotonin is reduced by at least 80% in the brain of said mouse as compared to a wild-type mouse. 
     
     
       10. The transgenic mouse of  claim 1 , wherein said transgene results in reduced levels of serotonin in the frontal cortex and hippocampus of said mouse as compared to a wild-type mouse. 
     
     
       11. The transgenic mouse of  claim 1 , wherein said transgene results in increased immobility in a tail suspension test as compared to a wild-type mouse. 
     
     
       12. The transgenic mouse of  claim 11 , wherein said transgene does not result in a decrease in basal locomotion measured by an open field test as compared to a wild-type mouse. 
     
     
       13. The transgenic mouse of  claim 11 , wherein said transgene results in reduced lever pressing in an operant behavior for food reward test as compared to a wild-type mouse. 
     
     
       14. The transgenic mouse of  claim 1 , wherein said mouse is an adult. 
     
     
       15. A progeny mouse of the transgenic mouse of  claim 1 . 
     
     
       16. The mouse of  claim 15 , wherein said mouse is a congenic mouse. 
     
     
       17. A cell isolated from the transgenic mouse of  claim 1 , wherein said cell comprises said transgene. 
     
     
       18. The cell of  claim 17 , wherein said cell is a central nerve cell. 
     
     
       19. A cell culture produced by culturing the cell of  claim 17 . 
     
     
       20. A cell culture produced by culturing the cell of  claim 18 . 
     
     
       21. A transgenic mouse comprising a mouse R439H mutant tryptophan hydroxylase 2 (Tph2) transgene, which replaces endogenous Tph2 in the genome of said mouse, wherein said mouse is heterozygous for the transgene, wherein said transgene results in reduced synthesis of 5-hydroxytryptophan (5-HTP) and reduced levels of serotonin in the brain of said mouse as compared to a wild-type mouse, and wherein said mouse exhibits a behavioral phenotype of a serotonergic neurotransmission dysregulation disorder. 
     
     
       22. The transgenic mouse of  claim 21 , wherein said serotonergic neurotransmission dysregulation disorder is depression. 
     
     
       23. The transgenic mouse of  claim 22 , wherein the behavioral phenotype of depression comprises behavioral despair. 
     
     
       24. The transgenic mouse of  claim 23 , wherein behavioral despair is evidenced by increased immobility in a tail suspension test as compared to a wild-type mouse. 
     
     
       25. The transgenic mouse of  claim 21 , wherein the synthesis rate of 5-HTP is reduced by at least 40% in the brain of said mouse as compared to a wild-type mouse. 
     
     
       26. The transgenic mouse of  claim 21 , wherein said transgene results in reduced synthesis of 5-HTP in the frontal cortex and hippocampus of said mouse as compared to a wild-type mouse. 
     
     
       27. The transgenic mouse of  claim 21 , wherein the synthesis rate of serotonin is reduced by at least 40% in the brain of said mouse as compared to a wild-type mouse. 
     
     
       28. The transgenic mouse of  claim 21 , wherein said transgene results in reduced levels of serotonin in the frontal cortex of said mouse as compared to a wild-type mouse. 
     
     
       29. The transgenic mouse of  claim 21 , wherein said transgene results in increased immobility in a tail suspension test as compared to a wild-type mouse. 
     
     
       30. The transgenic mouse of  claim 29 , wherein said transgene does not result in a decrease in basal locomotion measured by an open field test as compared to a wild-type mouse. 
     
     
       31. The transgenic mouse of  claim 21 , wherein said mouse is the progeny of a transgenic mouse expressing a mutant Tph2 transgene. 
     
     
       32. The transgenic mouse of  claim 21 , wherein said mouse is an adult. 
     
     
       33. A progeny mouse of the transgenic mouse of  claim 21 . 
     
     
       34. The mouse of  claim 33 , wherein said mouse is a congenic mouse. 
     
     
       35. A cell isolated from the transgenic mouse of  claim 21 , wherein said cell comprises said transgene. 
     
     
       36. The cell of  claim 35 , wherein said cell is a central nerve cell. 
     
     
       37. A cell culture produced by culturing the cell of  claim 35 . 
     
     
       38. A cell culture produced by culturing the cell of  claim 36 . 
     
     
       39. A method of screening a compound for serotonergic activity, comprising:
 administering a test compound to a transgenic mouse according to  claim 1 ; and then 
 detecting, in said mouse, the presence or absence of serotonergic activity in a biochemical assay or behavioral test. 
 
     
     
       40. The method of  claim 39 , wherein said compound is a selective serotonin reuptake inhibitor. 
     
     
       41. The method of  claim 39 , wherein said detecting step is carried out by performing a behavioral test selected from the group consisting of a tail suspension test, a forced swim test, a learned helplessness test, a fear conditioning test, a resident intruder test, a water maze test, a radial maze test, an operant conditioning test, a self-administration test, an open field locomotion test, a place preference test, a zero maze test, a latency to feeding test, a shock escape test and an open field exploration test. 
     
     
       42. A method of screening a compound for activity in treating a serotonergic neurotransmission dysregulation disorder, comprising:
 administering a test compound to a transgenic mouse according to  claim 1 ; and then 
 detecting, in said mouse, the presence or absence of activity in treating a serotonergic neurotransmission dysregulation disorder. 
 
     
     
       43. The method of  claim 42 , wherein said compound is a selective serotonin reuptake inhibitor. 
     
     
       44. The method of  claim 42 , wherein said detecting step is carried out by performing a behavioral test selected from the group consisting of a tail suspension test, a forced swim test, a learned helplessness test, a fear conditioning test, a resident intruder test, a water maze test, a radial maze test, an operant conditioning test, a self-administration test, an open field locomotion test, a place preference test, a zero maze test, a latency to feeding test, a shock escape test and an open field exploration test.